DRAFT
The NELAC Institute Presents:
SUGGESTED PROCEDURES FOR
LOQ
TNI plays well with Others…
These suggested procedures are compliant with
NELAC and TNI standards, and can provide a
dataset suitable for other Quantitation Limit
protocols, including:
 Detection/Quantitation Federal Advisory
Committee procedure
 Office of Water MRL
 Texas PQL
 DoD QSM v4.1
TNI DEFINITION - LOQ
Limit of Quantitation
The minimum levels, concentrations, or quantities
of a target analyte that can be reported with a
specified degree of confidence.
What is a TNI LOQ?
I see some yellow pollen on the stamens below. This
magnification is at my Limit of Detection (LOD). If it
were any smaller I wouldn’t see the pollen.
Magnif
Magnification – 2x
How many pollen particles do I see? (quantitate?)
I think maybe 3…
TNI DEFINITION - LOQ
I wasn’t really sure at 2x how many pollen
particles there were. But at 5x I am sure I am
reliably quantitating
Magnification – 5x
LOD is 2x (I can see it)
LOQ is 5x (I can reliably quantitate)
Exceptions for
LOQ
An annual LOQ verification
is not required if the LOD was
already determined or verified
annually on that instrument.
Requirements:
All sample processing steps must be included in
the determination of the LOQ
Requirements:
An LOQ verification study is not required for
any component or property for which spiking
solutions or quality control samples are not
available or otherwise inappropriate.
Such as pH or temperature.
Requirements:
The LOQ verification sample:
a. Must be spiked at 1-2 times the claimed LOQ,
b. And recovery must be within established control limits.
Limits
Result
50 – 150%
94%
percent
VERIFIED
120
110
100
90
80
LOQ Verification Spike
LOD
LOQ
2xLOQ
concentration
Requirements:
The LOQ verification sample:
a. Must be spiked at 1-2 times the claimed LOQ,
b. And recovery must be within established control limits.
percent
Limits Whatever
89.375
50
+/–is-–107.6
3125%
150%
SD %
reasonable!
Result
94%
120
110
100
90
80
LOD
LOQ
2xLOQ
concentration
Requirements:
When an LOD is determined or verified by the
laboratory, the LOQ shall be above the LOD.
Translation: They can not be the same number
zero
LOD
LOQ
If you don’t require an LOD,
then you don’t have to check
that your LOQ is greater than
your LOD!
Requirements: What?
Verify LOQ annually
…In each quality system
matrix AND for each
technology…
ON EACH INSTRUMENT??
Requirements:
Document your procedures
for LOQ determination and
verification for each quality
My Quality Manual
or SOP
system matrix type.
How my LOQ is determined in:
a. Water
b. Sediment
c. Tissue
Please be sure to check the
appropriate TNI module for analysisspecific LOD or LOQ requirements
Recommendation:
Because your lowest calibration standard will be your
LOQ concentration or lower, pick an LOQ that will pass
calibration criteria.
LOQ
Recommendation:
If you have an LOD that is about as low
as you can go, then pick an LOQ that is at
least 2 x your LOD
LOD LOQ
Q:
A:
Can your LOQ be
anything you want?
As long as it is greater than your LOD.
And it meets all client or program requirements…
Recommendation:
If you want to comply with other programs that require
multiple spikes for verification, we recommend you first
test with just one spike. If the LOQ was too low, you
didn’t waste time or money preparing the rest.
Recommendation:
To be compliant with other programs by analyzing
multiple LOQ spikes, we recommend…
Analyzing at least 2 replicates on each instrument for
a total of at least 7 replicates.
Replicates should not all be analyzed in a single
batch – a more representative data set is obtained if
the samples are spread over time.
Thought:
If you make an LOQ spike part of your routine quality
assurance, you won’t have to bother doing a separate
study at the end of the year.
REVIEW: Your TNI LOQ wish-list
…something that
Something
meetsabout
program
twice the
LOD
would
…ohhhh.
And
don’t
forget
and customer
different matrices
or technologies.
berequirements….
nice….
If this LOQ …something
won’t pass forthat
them
can be
(even thoughverified
it’s the on
same
each
…maybe
something
that
analyte),
I may
require
a separate
instrument…
would
pass
LOQ
forcalibration
those.
criteria and…
end